Theres an intersteing article in this months issue of Model Aviation. IMO its a must read for anyone with prop issues or questions. It's called "From the Ground Up" and it can be found on their website if you dont have the magazine. Most of what was written I agreed with, but I had issues with prop loading in the air. They claim that an engine will lean approx 500 rpms in the air I think is more like 1000 but in either case I would rather over estiamte that number. Prop size is discussed in detail what should be looked for what type of flying do you want to do and how your engine should respond given the different prop sizes for your size engine. Peak RPM as opposed to Peak power out put RPM both different. Where your engine revs to peak RPMs but you get no more power then say 1500 (as an example it may be less) rpms before. Its just wasted RPMs. I found it to be very very informative IMO. Hope this helps.